Such a self-locking step-by-step switching mechanism is known from DE 195 40 631 C2. The clamping roller lock used in this case is also referred to as a freewheel. Such clamping roller locks are known from DE 10 2010 43 825 and DE 10 2010 031 133. Other step-by-step switching mechanisms are known from DE 44 00 910 A1 and DE 43 44 225 A1.